Arc-lamp.



E. J. GUAYk ARC LAMP.

APPLICATION FILED 1AN.3I. 1911.

1,276,522. Patented Aug. 20, 1918.

Fig.1.

Inventor: Emile JGuag,

' His o t corneg.

UNITED STATES PATENT OFFICE.

EMILE J. GUAY, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

ARC-LAMP.

Specification of Letterslatent. Patented Aug. 20, 1918.

Application filed January 31, 1917. Serial No. 145,779.

To all whom it may concern:

Be it known that I, EMJLE J. GUAY, a c1t1- zen of the United States,residing at Lynn, in the county of Essex, State of Massachusetts, haveinvented certain new and useful Improvements in Arc-Lamps, of which thefollowing is a specification.

My invention has reference to alternating current are lamps fed from aconstant current supply system through the intermediary of atransformer, preferably an autotransformer. The invention is especiallyuseful in connection with are lamps of the character known as luminousarc lamps, employing one metallic and one carbon electrode. In suchlamps, and also in ordinary flame lamps it occurs or may occur that afilm of insulating matter is formed at the arcing face of one or bothelectrodes, so that the starting of the arc, when the electrodes arecold, is difficult or uncertain with the normal arc voltage. In bothkinds of lamp, but especially in luminous arc lamps, the arc is slenderand is subject to fluctuations, due to the fact that at each reversal ofcurrent the arc has to start anew, sometimes from a comparatively hotand sometimes from a comparatively cold point of the respectiveelectrode. The resistance of the arc may also Vary suddenly within widelimits, and, therefore, being fed by a constant current, the differenceof potential between the electrodes would vary suddenly within widelimits, especially when, by the consumption of the electrodes, the arcis lengthened. WVhen this happens the maintenance of the are by theenergy supplied to it becomes uncertain and the arc is liable tocollapse, and at such times it is necessary to bring the are again to astable condition. In the case of luminous arc lamps this is done bybringing the electrodes together and again reestablishing the normalarc. After this has been done, the old play begins again; that is tosay,-the are again gradually becomes fluctuating and unsteady and,

in the case of luminous arc lamps, it has to be extinguished andreestablished as before.

Such, or similar operation, whereby the arc is restored to its normallength and condition, is called a feeding operation.

In accordancewit-h my invention the feeding operation is induced by anelectromagnet in a virtual or actual shunt around the arc, which shunt,however, is open before the arc is established and is only closed by theestablishment of the arc and is then not sufiiciently energized toinduce a feeding operation until the arc becomes unduly long,fluctuating and unsteady and diverts a high potential to the shuntmagnet. By the use of such shunt magnet which is on open circuit beforethe arc is established the secondary of the transformer through whichcurrent is supplied to the electrodes can attain a higher difference ofpotential than if the electromagnet were in a constantly closed shuntand this extraordinary high potential serves to break through anyinsulating film that may have formed between the electrode faces,whereby the initial starting of the arc is insured. Allthis will morefully appear from the following detailed description with reference tothe accompanying drawing in which Figure l is a skeleton view of aluminous arc lamp embodying my invention and Fig. 2 is a diagram of amodification thereof.

Referring now particularly to Fig. 1, the lower electrode 1 is themetallic electrode of a luminous arc lamp, preferably made of titaniumcarbid, such as isproduced in an arc furnace and which contains anexcess of titanium. The upper electrode 2 is hereshown as made ofcarbon. These two electrodes with their holders are here shown asconnected through a chain 3, or other flexible medium which passes overa sheave 4, whichis journaled on a lever 5, which is fulcrumed at 5, andwhich at one end is connected with the armature 6, of the serieselectromagnet 7, and at the other end with the barrel of a dash-pot 8,the piston 9 of which is fixed to some part of the frame of the lamp.The weights of the upper and lower electrodes and of their holders andappurtenances are so proportioned that the upper electrode, even whenlargly consumed preponderates, so that when the sheave is free to rotatethe two electrodes will come together.

Lamps of this character are designed to be focusing lamps and wlienfedby alternating currents the electrodes, if both are of the samematerial, are consumed about equally; but since in the case here shownthe upper electrode is made of carbon, it will consume faster than thelower electrode and it is therefore given a larger diameter than thelower electrode, so that about equal lengths of both electrodes will beconsumed. For this reason the flexible connection 3 between the twoelectrodes is 7 would be secured to a sheave of somewhat larger diameterthan the flexible connection from the lower electrode. These are matterswell understood in the art and need not be here dwelt upon.

On the lever 5 is pivoted abrake shoe 10, the bearing face of which isadapted to engagethe inner surface of the projecting rim 11 of thesheave. In consequence of this construction, when the armature of theelectromagnet'? is raised the brake shoe clamps the sheave, which isthus partially rotated to separate the electrodes. hen, on the otherhand, the armature of the electromagnet 7 descends, as itwill when thereis no current through the magnet coil, the brake shoe releases. thesheave and the electrodes are free to come together by the preponderanceof the weight of the upper electrode and its holder.

On the left-hand side of the lever 5, between the sheave 1 and thebarrel 8 of the dash-pot, there is adjustably secured an eccentric 12,from which a spur extends downwardly in such position that when the leftside of the lever 5 descends, this spur will bear upon a strip 1 1extending from a contact 15, which is fixed to some stationary part ofthe lamp frame.

' The electromagnet 16 has a core or armature 17, which, when there isno current through the magnet winding is in the lowest position shown inthe drawing; it carries a movable contact 18 ust below and in alinementwith the fixed contact 15. If the" electromagnet 16 1s sufiicientlyenergized its core or armature will rise and the contact 18 rising withit will bear'upon the fixed contact 15. i

The circuit connections are as follows: The constant current lineterminals 19, 20 are connected with the primary 21 of a stepuptransformer, the secondary 22 of which is connected at one one vith oneterminal of the series magnet winding 7 by conductor 23 and at the otherend with the lower electrode holder by conductor The other terminal ofthe electromagnet winding 7 is connected with the upper electrode holderby a conductor 25.. The line is also connected onone side by conductor:26 to the eccentric 1:2 and at the other side by conductor 27with oneterminal of the electromagnet winding 16, the other terminal of which isconnected by conductor 28, with the stationary contact 15. In additionto this, there is a cross-connection between the movable contact 18andthe conductor 27 by a conductor 29.

The operation of a lamp thus equipped is as follows: When there is nocurrent on the lamp the electrodes are in contact, as shown in thedrawing, and there may or may not be an insulating film on one or bothelectrode faces, and if there is such a film the secondary of thetransformer is on open circuit. At this stage the magnet 16 is also onopen circuit, since the spur 13 of the eccentric 12 is out of contactwith the strip 14. Now when current is turned on to the lamp from aconstant current supply, a high difference of potential is establishedbetween the terminals of the secondary of the transformer and betweenthe electrodes. This difference ofpotential is greater than would be thecase if the circuit of the electromagnet 16 which actually shunts theprimary and virtually shunts the secondary of the transformer wereclosed, and this potential is exceptionally high when there is aninsulating film between the electrode faces. Therefore, a high potentialdischarge between the electrodes passes and breaks through anyinsulation which may there exist. The current now flows through theelectromagnet 7, the armature or core 6 of which is thereby raised, andthe right-hand end of the lever 5 is elevated, whereby the brake shoe10, gripping the rim of the sheave 4 rotates the lattercounter-clockwise, whereby the electrodes are separated and the arc isestablished. Toward the end of this movement the spur 13 comes intocontact with the strip 14 and therebycloses the circuit through theshunt magnet 16 as follows:

From line 19 by conductor 27 to and through electromagnet 16, byconductor 28,

contact 15, strip 141 to spur 13 of eccentric 12, and by conductor 26 toline 20. At this time the are has its normal length and the transformerfully loaded; therefore, the potential difference between the lineterminals is comparatively small. Ihe winding of electromagnet 1.6 is sodesigned that under these normal conditions it receivesinsuflicientcurrent to raise its core. The lamp, therefore, continues tooperate, starting with a normal arc, which, however, by. consumption ofthe electrodes, becomes eventually unsteady and fluctuating and thedifference of potential between the line terminals becomes high enoughto pass through the electromagnet 16 suflicient current to raiseits core17 and to establishcontaet between the movable contact 18 and the fixedcontact 15; As soon as this happens the current is diverted from themagnet 16 bythe short-circuiting conductor 29, and this not onlyactually short-circuits the magnet 16, but also the primary of thetransformer and thereby virtually short circuits the arc and the arcestablishing magnet. The lamp is thereby deprived ofcurrent, thearcbreaks,

the electromagnet 7 is deenergized, its core drops and by the downwardmovement of the lever 5 at the right-hand end the brake shoe 10 releasesthe rim 11 of the sheave 4, so that the latter is now free to rotate andthe electrodes come together. The next instant, however, the arc isagain established as before. It will'thus be seen that by the attainmentof a high difference of potential between the line terminals, when theare becomes too long or for any other reason, the short circuiting ofthis shunt magnet induces a feeding operation which, in the constructionhere shown, consists in eXtinguishing the are by a short circuit andreestablishing the same to normal condition; the magnet 16, therefore,controls the feeding of the electrodes.

The circuit connections may be varied without deviating from myinvention in several ways, one of which is diagrammatically indicated inFig. 2, where all the parts are supposed to be the same as those shownin Fig. 1, except that the feed control magnet 16 is in a shunt aroundthe secondary of the transformer and the short circuit around thecontrol magnet is also in a shunt to the secondary of the transformer.

An ordinary transformer may be used, but the drawing shows thepreferable form, namely an auto-transformer.

It will now be understood that this invention is applicable to allalternating current are lamps in which unduly high voltage peaks mayoccur, no matter whether these high voltage peaks be due to the natureof the electrodes employed or to other causes.

It will also be understood that the ultimate effect upon the operationof the lamp is the same whether the shunts and shortcircuits hereinreferred to are actual or virtual shunts and short-circuits, so that theterms shunt and shortcircuit in the appended claims have the genericsignificance.

WVhat I claim as new and desire to secure by Letters Patent of theUnited States is:

1. The method of operating an arc lamp from a constant alternatingcurrent line, which consists in momentarily inducing-by the line currenta sufliciently high potential discharge between the contactingelectrodes to puncture any intervening insulating film and separatingthe electrodes to establish the are, then and thereby partiallyshort-circuiting the electrodes and reducing the voltage between them tothat requisite to maintain a normal length of arc, and deadshort-circuiting the electrodes and thereby causing a feeding operationwhen an unduly high voltage peak occurs.

2. The method of operating arc lamps from a constant alternating currentline through the medium of a step-up transformer, which consists incharging the primary of the transformer with the full line current andthereby inducing in the secondary circuit and between the contactingelectrodes a sufficiently high potential discharge to puncture anyintervening insulating film and separating the electrodes to establishthe arc, then and thereby reducing the primary charge and the arcvoltage to that suitable to maintain a normal length of arc, and deadshort-circuiting the primary and thereby causing a feeding operationwhen an unduly high voltage peak occurs.

3. An arc lamp for an alternating constant current supply line,comprising a stepup transformer the primary of which is in the line andthe secondary in the electrode circuit, an arc establishing magnet inthe electrode circuit, a normally open circuited feed control magnetsubjected to variations of potential corresponding to those in theelectrode circuit, means actuated by the arc establishing magnet forclosing the circuit of the feed control magnet, and means forshort-circuiting the control magnet in response to an unduly highpotential discharge through the same.

4. An arc lamp for an alternating constant current supply line,comprising a stepup transformer the primary of which is in the line andthe secondary in the electrode circuit, an arc establishing magnet inthe electrode circuit, a magnet in a normally open shunt across theprimary of the transformer, means actuated by the arc establishingmagnet for closing the shunt circuit, and means for short-circuiting theprimary of the transformer in response to an unduly high potentialdischarge through the shunt magnet.

5. An alternating current arc lamp having electrodes which always tendto and which are in contact when there is no current through the lamp; astep-up transformer, the primary of which is in a constant currentsupply circuit, and the secondary of which is in the electrode circuit;a series electromagnet in the electrode circuit for establishing the areby the energy conveyed by the secondary of the transformer; a shuntmagnet, the circuit of which is normally open; means for closing theshunt circuit by the arc establishing means, and means for inducingthrough the shunt magnet an electrode feeding operation by the seriesmagnet when an unduly high voltage peak occurs at the are.

6. An alternating current are lamp having electrodes which alwiys tendto and which are in contact when there is no current through the lamp; astep-up transformer, the primary of which is in a constant currentsupply circuit and the secondary of which is in the electrode circuit; aseries electromagnet in the electrode circuit for establishing the areby the energy conveyed by the secondary of the transformer; a shuntmagnet the circuit of which is normally open means for closing the shuntcircuit by the arc establishing means; means for short-circuiting thetransformer by the shunt magnet When an unduly high voltage peak occursat the arc and thereby deenergizing the series magnet and allowing theelectrodes to come into contact, whereby the initial condition of thelamp is restored and the arc is reestablished to normal length. 7 10 InWitness whereof I have hereunto set my hand this 29th day of January,1917.

EMILE J. GUAY.

Copies of this patent may be obtained for 'five cents each, byaddressing .the Commissioner of Patents,

Washington, D. .0.

